Dental impression material



an elastic gel.

Patented Sept. 15, 1953 2,652,312 DENTALIMPRESSION MATERIAL Arthur Fink,New York, N. Y., assignorto Plastodent, Inc., New York, N. Y., acorporation of New York No Drawing. Application July 8, 1953, Serial No.366,904. In Canada December 23, 1952 8 Claims. 1

This invention relates to dental impression compositions andparticularly to such material employing an alginate in admixture withother salts.

These compositions are of the type set forth in Letters Patent No.2,422,497, granted June 17, 1947, to Stanley E. Noyes and comprising analginate salt, a gelling agent such as a calcium sulphate, leadsilicate, etc. reactive with the alginate, a filler such as diatomaceousearth, and a control or retarder such as a fiuosilicate, phosphate, etc.

Such compositions when brought into contact with water are formed into apasty mass which when introduced into the mouth will harden intoSubsequently a casting is made by pouring another hardening mixture intothe impression acting as a mold and this casting is used in theformation of the final denture.

Prior impression compositions have proven disadvantageous in a tendencyof the dry mixture to absorb moisture and cake up, making it difiicultto mix. After the impression is taken, it must be promptly used becausedimensional changes with loss of water occur and the gel tends to besoft with a weak body, and the dental stone or plaster of Paris cast inthe impression has a soft powdery surface which interfere with thefaithful reproduction of details.

I have found that such alginate compositions are improved by thepresence of a minor amount of an alkali metal titanium fluoride or analkali metal zirconium fluoride and in particular a zirconium ortitanium fluoride of sodium or potassium. A small percentage, forinstance, of 1% to 7% of such alkali metal fluoride gives greatlyimproved shelf life to the dry mixture; and controls the setting actionby regulating it to just the right length of time; the impression takenwith .the wet mixture has a tough, strong body and ma remain in waterfor hours with no dimensional changes and it produces cast models withsmooth, hard surfaces.

A typical embodiment using a filler powder, for instance, diatomaceousearth (about half, 51%), includes 13% potassium alginate, 7.2% calciumsulphate (partially dehydrated preferably to CaSO4. /2HzO), 24.4% leadsilicate, 2.6% potassium titanium fluoride, and preferably 1.8%trisodium phosphate.

Any other alkali metal fluoride of titanium or zirconium, particularlysodium titanium fluoride or sodium or potassium zirconium fluoride, maybe substituted in place of the potassium titanium fluoride. Theproportion of fluoride should not be reduced below of 1% but preferablyis kept below 7%. It also preferably replaces the fluosilicatefrequently employed in prior alignate compositions, such fluosilicatebeing objectionable in exercising an insufficient control of the rate ofsetting and in not giving sufficient strength or body to the impression.

The partially dehydrated calcium sulphate is preferably in the range of2 to 10% and combines with the alginate and fluoride filler and thiscombination imparts to the mixture a smooth texture which sets promptlyin several minutes in the mouth to an elastic gel easily stripped fromthe teeth and accurately preserving the impression.

Lead silicate may be added to the composition in varied proportion, 20%to 40%, for instance, preferably being less than half so that it is inminor proportion; and other silicates such as calcium silicate may beused.

The sodium phosphate, represented, for instance by trisodium phosphatein the formula, is preferably within the range of 1 to 5%.

When omitting the fluoride, the material tends to set too slowly anddoes not have the desired strength and body. Since it is most importantthat the gel should set in the mouth Within several minutes and that itshould form a strong elastic mass, it is clear that the addition of thefluoride is of prime importance.

As noted above, the filler may be in relatively large proportionconstituting about half (40 to of the composition and other powders,such as chalk, silica, clay, etc., may be used instead of diatomaceousearth. In all variations the fluoride may be used to control thecharacteristics of the impression material and accelerate the reactionto give the desired time of setting and produce a composite formationsafely retaining the wetting liquid and holding it against oozing ordripping off onto the patients tongue in a manner likely to causegagging. The impression also has body, resilience, strength and accuratesurfacing in the final mass as it is removed from the mouth of thepatient.

I claim:

1. A dental impression composition comprising a water-soluble alginate,a gel forming agent reactive therewith to form the composition into anelastic gel, a filler, and a fluoride of the group consisting of analkali metal titanium fluoride and an alkali metal zirconium fluoride.

2. A dental impression composition as set forth in claim 1 in which thefluoride is of the group consisting of sodium titanium fluoride,potassium 3 titanium fluoride, sodium zirconium fluoride, and potassiumzirconium fluoride.

3. A composition as defined in claim 2 in which the fluoride ispotassium titanium fluoride.

4. A composition as defined in claim 2 containing also an alkali metalphosphate salt.

5. A composition as defined in claim 2 containing also lead silicate.

6. A dental impression composition comprising a water-soluble alginate,calcium sulphate reactive therewith to form the composition into anelastic gel, a filler material constituting between about 40% to 60% ofthe composition, and potassium titanium fluoride constituting about /2%to 7% of the composition.

'7. A dental impression composition comprising a water-soluble alginate,calcium sulphate reactive therewith to form the composition into anelastic gel, a phosphate salt, between about /2% to 7% of potassiumtitanium fluoride, and between about 40% to 60% of a filler.

8. A dental impression composition comprising a water-soluble alginate,calcium sulphate reactive therewith to form the composition into anelastic gel, a phosphate salt, between about /2% to 7% of sodiumtitanium fluoride, and between about 40% to 60% of a filler.

ARTHUR FINK.

No references cited.

1. A DENTAL IMPRESSION COMPOSITION COMPRISING A WATER-SOLUBLE ALGINATE,A GEL-FORMING AGENT REACTIVE THEREWITH TO FORM THE COMPOSITION INTO ANELASTIC GEL, A FILLER, AND A FLUORIDE OF THE GROUP CONSISTING OF ANALKALI METAL TITANIUM FLUORIDE AND AN ALKALI METAL ZIRCONIUM FLUORIDE.